Laser annealing apparatus and method of fabricating thin film transistor

ABSTRACT

In a method of fabricating a thin film transistor through conversion of an amorphous silicon film into a polysilicon film to be an active layer of the thin film transistor by a laser annealing treatment, a laser annealing apparatus comprising a plurality of semiconductor laser devices arranged performs the laser annealing treatment by irradiating the surface of the amorphous silicon film with laser light uniformized in the light intensity of the laser light radiated onto the surface of the amorphous silicon film, whereby the crystal grain diameter of the polysilicon film obtained through recrystallization is uniformized, and it is possible to obtain a thin film transistor with transistor characteristics enhanced by using the polysilicon film as the active layer.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a laser annealing apparatus forapplying an annealing treatment to a material by irradiating the surfaceof the material with laser light, and a method of fabricating a thinfilm transistor by converting an amorphous silicon film to apolycrystalline silicon film which becomes an active layer of the thinfilm transistor through an annealing treatment.

[0002] The thin film transistor is widely used as a switching device ina liquid crystal display. Where polycrystalline silicon (hereinafterreferred to as polysilicon) film is used as a channel layer in the thinfilm transistor, the electrolytic mobility of the thin film transistoris very high, so that the thin film transistor can be incorporated, forexample, as a driving circuit in a liquid crystal display, and it ispossible to realize higher definition, smaller size and the like of thedisplay.

[0003] In addition, the thin film transistor using a polysilicon film asthe channel layer has a higher driving current, as compared with thecase where an amorphous silicon film is used as the channel layer, sothat the thin film transistor can be applied to a pixel transistor in anorganic electroluminescence (hereinafter abbreviated to EL) displayutilizing EL of an organic material using a current driving system.

[0004] As a method for forming a polysilicon film on an insulatingsubstrate, there is a method of converting an amorphous silicon filmformed on the surface of an insulating substrate formed of, for example,glass, quartz, etc. into a polysilicon film by subjecting the amorphoussilicon film to a laser annealing treatment through irradiation withlaser light by use of a laser annealing apparatus.

[0005] The laser annealing apparatus used for the laser annealingtreatment uses an excimer laser as a light source of the laser light.The excimer laser emits laser light at an ultraviolet wavelength in apulsed state, and, since silicon has a high absorption coefficient forthe laser light at the ultraviolet wavelength emitted in the pulsedstate, an efficient laser annealing treatment of an amorphous siliconfilm can be achieved.

[0006] The laser annealing treatment is conducted in such a manner thatthe laser light emitted from the excimer laser is processed by, forexample, a beam homogenizer to form the irradiation plane relative tothe amorphous silicon surface into a linear form, and the amorphoussilicon is polycrystallized into polysilicon while moving theirradiation region of the laser light. At the time of performing thelaser annealing treatment, the laser light is scanned in a directionorthogonal to the longitudinal direction of the irradiation plane of thelaser light formed in the linear form.

[0007] In the laser annealing apparatus described above, however, thepulsed emission of the laser light from the excimer laser is performedthrough excitation of an excitable gas such as XeCl and KrF, so that theemission of the laser light will easily become unstable attendant ondeterioration of the excitable gas, and the light intensity of the laserlight on a pulse basis may be dispersed.

[0008] In this laser annealing apparatus, therefore, the laser annealingtreatment of the amorphous silicon film is conducted with the laserlight dispersed in light intensity, resulting in a laser annealingtreatment in which the heated and molten state of the amorphous siliconfilm is dispersed.

[0009] Therefore, with the amorphous silicon film of which the heatedand molten state is dispersed, the grain size of crystal grains in thepolysilicon film obtained through recrystallization is dispersed. Thus,there has been the problem that nonuniformity in the form of, forexample, streaks or spots, is generated in the picture formed by displaydevices, and transistor characteristics are deteriorated.

[0010] In addition, in the laser annealing apparatus as above, the stepof gas replacement attendant on the deterioration of the excitable gasused in the excimer laser leads to a lowering in productivity and anincrease in the cost of production of the thin film transistor.

[0011] Furthermore, the laser annealing apparatus needs a tank forstoring the excitable gas, and is large in the size of equipment.Therefore, the laser annealing apparatus leads to a large installationarea and a large power consumption, resulting in an increase in the costof production of the thin film transistor.

SUMMARY OF THE INVENTION

[0012] The present invention has been proposed in consideration of theabove situations. Accordingly, it is an object of the present inventionto provide a laser annealing apparatus capable of an annealing treatmentwith stable light intensity, and a method of fabricating a thin filmtransistor which makes it possible to enhance transistorcharacteristics, to enhance productivity and to reduce production costby using a polycrystalline silicon film obtained through the annealingtreatment by laser light with the stable light intensity.

[0013] In accordance with one aspect of the present invention, there isprovided a laser annealing apparatus for subjecting a material to anannealing treatment by irradiating the surface of the material withlaser light, comprising a plurality of semiconductor laser devices foremitting laser light toward the material, and unformizing means foruniformizing the light intensity of the laser light emitted from theplurality of semiconductor laser devices and radiated to the surface ofthe material.

[0014] In the laser annealing apparatus, the laser light emitted fromthe plurality of semiconductor laser devices is processed by theuniformizing means so that the light intensity of the laser light withwhich the surface of the material is irradiated is uniformized, to thatit is possible to subject the material to an annealing treatment by thelaser light with a stable light intensity.

[0015] According to the present invention, therefore, dispersion of theheated and molten state of the amorphous silicon film can be restrained,the grain diameter of crystal grains of the polycrystalline silicon filmrecrystallized from the amorphous silicon film is uniformized, andtransistor characteristics of the thin film transistor comprising thepolycrystalline silicon film as an active layer can be enhanced.

[0016] In accordance with another aspect of the present invention, thereis provided a method of fabricating a thin film transistor whichcomprises a first step of forming an amorphous silicon film on asubstrate, a second step of subjecting the amorphous silicon film to anannealing treatment to thereby convert the amorphous silicon film into apolycrystalline silicon film, and a third step of laminatinglyfabricating the thin film transistor in a predetermined region with thepolycrystalline silicon film as an active layer. In the method offabricating a thin film transistor, in the second step, the laserannealing apparatus comprising a plurality of semiconductor laserdevices for emitting laser light subjects the surface of the amorphoussilicon film to the annealing treatment while uniformizing the lightintensity of the laser light radiated onto the surface of the amorphoussilicon film by uniformizing means for uniformizing the light intensityof the laser light radiated onto the surface of the amorphous siliconfilm, whereby the amorphous silicon film is heated, melted andrecrystallized to be thereby converted into the polycrystalline siliconfilm.

[0017] According to the method of fabricating a thin film transistor,the laser annealing apparatus subjects the amorphous silicon film to theannealing treatment while processing the laser light emitted from theplurality of semiconductor laser devices by the uniformizing means so asto uniformize the light intensity of the laser light with which thesurface of the amorphous silicon film is irradiated. Therefore,dispersion of the heated and molten state of the amorphous silicon filmis restrained, the grain diameter of the crystal grains of thepolycrystalline silicon film recrystallized from the amorphous siliconfilm is uniformized, and a thin film transistor with enhanced transistorcharacteristics can be obtained.

[0018] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionand appended claims, taken in conjunction with the accompanying drawingswhich show by way of example some preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 illustrates a schematic sectional structure of a thin filmtransistor;

[0020]FIG. 2 is a general perspective view for illustrating theconstitution of a laser annealing apparatus according to one embodimentof the present invention;

[0021]FIG. 3 is a characteristic diagram showing the relationshipbetween wavelength of laser light and absorption coefficients ofpolysilicon and amorphous silicon;

[0022]FIG. 4 is a general perspective view for illustrating anotherconstitution of the laser annealing apparatus according to oneembodiment of the present invention;

[0023]FIG. 5 is a general perspective view for illustrating a furtherconstitution of the laser annealing apparatus;

[0024]FIG. 6 is a general perspective view for illustrating stillanother constitution of the laser annealing apparatus;

[0025]FIG. 7 is a general perspective view for illustrating a stillfurther constitution of the laser annealing apparatus; and

[0026]FIG. 8 is a general perspective view for illustrating anotherconstitution of the laser annealing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Now, as an embodiment of the present invention, a laser annealingapparatus and a method of fabricating a thin film transistor accordingto the present invention will be described.

[0028] The laser annealing apparatus according to the embodiment of thepresent invention is used for a laser annealing treatment applied to anamorphous silicon film at the time of converting the amorphous siliconfilm into a crystalline silicon (hereinafter referred to as polysilicon)film through heating, melting and recrystallization by a laser annealingtreatment of the amorphous silicon film in the fabrication process of,for example, a thin film transistor (hereinafter referred to as TFT).The TFT has a structure in which a gate electrode, a gate insulator, anda polysilicon film (channel layer) are sequentially laminated on, forexample, a glass substrate from the lower side. Namely, the TFT has abottom gate structure in which the gate electrode is provided betweenthe polysilicon film, which functions as a channel layer, and the glasssubstrate.

[0029] A concrete constitution and a method of fabrication of the TFThaving the above-mentioned structure will be described referring to FIG.1.

[0030] As shown in FIG. 1, the TFT 1 has a constitution in which thegate electrode 3, a first gate insulation film 4, a second gateinsulation film 5, the polysilicon film 6, a stopper 7, a firstinter-layer insulation film 8, a second inter-layer insulation film 9, awiring 10, a planarizing film 11, and a transparent conductive film 12are laminated on the glass substrate 2.

[0031] In fabricating the TFT 1 constituted as above, first, a metallicfilm of, for example, molybdenum (Mo), aluminum (Al), tantalum (Ta),titanium (Ti), chromium (Cr), tungsten (W) is formed on the glasssubstrate 2, and the metallic film is patterned by anisotropic etchingto form the gate electrode 3.

[0032] Next, the first gate insulation film 4 formed of, for example,silicon nitride (SiN_(x)) is laminated on the glass substrate 2 providedthereon with the gate electrode 3.

[0033] Subsequently, the second gate insulation film 5 formed of, forexample, silicon dioxide (SiO₂) is laminated on the first gateinsulation film 4.

[0034] Next, the polysilicon film 6 formed of polysilicon, for example,is laminated on the second gate insulation film 5. The polysilicon film6 functions as a channel layer of a bottom gate type TFT 1, and isformed by forming an amorphous silicon film by, for example, an LPCVDmethod, and then subjecting the amorphous silicon film to a laserannealing treatment by irradiating the amorphous silicon with laserlight, thereby heating, melting and recrystallizing the amorphoussilicon film to convert it into a polycrystalline film.

[0035] In the step of polycrystallization for obtaining the polysiliconfilm 6, the laser annealing treatment for heating and melting theamorphous silicon film is conducted by use of a laser annealingapparatus 20 shown in FIG. 2.

[0036] The laser annealing apparatus 20 used in the present embodimentis comprised of a moving stage 21, semiconductor laser devices 22, asupport base 23, a control computer 24, and a power source 25.

[0037] The moving stage 21 is a mount base for mounting on its mainsurface the glass substrate 2 provided thereon with the amorphoussilicon film to be subjected to the laser annealing treatment. Themoving stage 21 is high in flatness of its main surface on which tomount the glass substrate 2, and has the function of moving the glasssubstrate 2 mounted thereon to the position for the laser annealingtreatment and the function of fixing the glass substrate 2.

[0038] In concrete, the moving stage 21 is comprised of an X stage 26, aY stage 27, and a sucker mechanism which is not shown. The X stage 26and the Y stage 27 are stages for horizontally moving the moving stage21 in the directions of arrow X and arrow Y in the figure in the planeof the main surface of the moving stage 21, whereby the glass substrate2 mounted on the moving stage 21 is moved in mutually roughly orthogonaldirections and led to the position for the laser annealing treatment.The sucker mechanism is for fixing the glass substrate 2 by sucking theglass substrate 2 onto the main surface of the moving stage 21.

[0039] The semiconductor laser devices 22 are laser light sources eachof which comprises an emitting portion 29 for emitting laser light 28for performing the laser annealing treatment of the amorphous siliconfilm, and in which a compound semiconductor of, for example, GaN, GaAsis used as an active layer. The semiconductor laser device 22 is notlimited to the one in which the compound semiconductor of GaN, GaAs orthe like is used as the active layer. For example, compoundsemiconductors obtained by synthesizing a compound comprised of any oneor a plurality of elements selected from the group consisting of Ga, Al,and In with a compound comprised of any one or a plurality of elementsselected from the group consisting of N, As, P, Zn, Se, Mg, Cd, and Smay also be used as the active layer in the semiconductor laser device22. Besides, in the semiconductor laser device 22, a compoundsemiconductor comprising SiC or diamond as a main constituent may beused as the active layer.

[0040] The support base 23 supports the plurality of semiconductor laserdevices 22 in series at predetermined intervals on the surface of theamorphous silicon film so that the emitting portions 29 for emitting thelaser light 28 and the surface of the amorphous silicon film are opposedin parallel to each other. In addition, the support base 23 comprises alift mechanism which is not shown so that the semiconductor laserdevices 22 supported thereon are vertically moved up and down as arrowsZ in the figure relative to the moving stage 21. The lift mechanism iscapable of regulating the distance between the plurality ofsemiconductor laser devices 22 and the surface of the amorphous siliconfilm, whereby the light intensity of the laser light 28 emitted from theplurality of semiconductor laser devices 22 and radiated onto thesurface of the amorphous silicon film is varied.

[0041] The control computer 24 performs, for example, control ofmovement of the moving stage 21, control of emission of the laser light28 at the semiconductor laser devices 22, control of the lift mechanismof the support base 23, and the like.

[0042] The power source 25 supplies, for example, electric power foremission of the laser light 28 from the semiconductor laser devices 22,and electric power for operating the control computer 24, to thesemiconductor laser devices 22 and the control computer 24 and the like.

[0043] In the laser annealing apparatus 20 constituted as above, thelaser light 28 emitted from the plurality of semiconductor laser devices22 is radiated onto the surface of the amorphous silicon film in such amanner that the light intensity of the laser light 28 is uniformized.

[0044] As the conditions for uniformizing the light intensity of thelaser light 28 with which the surface of the amorphous silicon film isirradiated, there may be mentioned, for example, the condition where theplurality of semiconductor laser devices 22 are supported on the supportbase 23 so that the distances between the emitting portions 29 of theplurality of semiconductor laser devices 22 and the surface of theamorphous silicon film are constant, the condition where the pluralityof the semiconductor laser devices 22 are arranged on the support base23 at such intervals that the laser light 28 radiated onto the surfaceof the amorphous silicon film does not contain overlaps of beams or gapsbetween beams, and the condition where the laser light 28 is emittedfrom the plurality of semiconductor laser devices 22 at the same lightintensity.

[0045] By this, in the laser annealing apparatus 20, the light intensityof the laser light 28 emitted from the plurality of semiconductor laserdevices 22 and radiated onto the surface of the amorphous silicon filmis uniformized, and the amorphous silicon film is irradiated with thelaser light 28 with the stable light intensity, so that the amorphoussilicon film can be heated and melted without dispersion.

[0046] At the time of forming the polysilicon film 6 by use of theabove-described laser annealing apparatus 20, first, the glass substrate2 provided thereon with the amorphous silicon film is mounted on themoving stage 21.

[0047] Next, the lift mechanism of the support base 23 supporting theplurality of semiconductor laser devices 22 thereon moves the supportbase 23 up or down relative to the moving stage 21, thereby regulatingthe distance between the plurality of semiconductor laser devices 22 andthe surface of the amorphous silicon film. By this, the light intensityof the laser light 28 emitted from the plurality of semiconductor laserdevices 22 and radiated onto the surface of the amorphous silicon filmcan be regulated to a desired intensity.

[0048] Subsequently, the laser light emitted from the plurality ofsemiconductor laser devices 22 is radiated onto the surface of theamorphous silicon film, and the moving stage 21 is brought into aparallel movement in a direction roughly orthogonal to the direction inwhich the plurality of semiconductor laser devices 22 are arranged inseries, whereby a laser annealing treatment for polycrystallizing theamorphous silicon film into the polysilicon film 6 is performed whilemoving the irradiation region of the laser light 28.

[0049] By performing the laser annealing treatment by irradiating thesurface of the amorphous silicon film with the laser light 28uniformized in the light intensity of the laser light 28 radiated ontothe surface of the amorphous silicon film in the above-mentioned manner,dispersion of the heated and molten state of the amorphous silicon filmis restrained, and the polysilicon film 6 uniformized in the graindiameter of crystal grains obtained through recrystallization is formed.

[0050] Next, as shown in FIG. 1, a film of, for example, silicon dioxide(SiO₂) is formed on the polysilicon film 6 formed in the above-mentionedmanner, and the film of silicon dioxide (SiO₂) is patterned, forexample, by the same patterning method as that used for forming the gateelectrode 3, whereby a stopper 7 is formed at a position correspondingto the gate electrode 3.

[0051] Subsequently, the polysilicon film 6 is doped with ions of animpurity for forming source/drain regions. At this time, the stopper 7prevents the polysilicon film 6 on the upper side of the gate electrode3 from being doped with the ions of the impurity.

[0052] Next, a first inter-layer insulation film 8 formed of, forexample, silicon dioxide (SiO₂) is laminated on the polysilicon film 6provided with the stopper 7.

[0053] Subsequently, a second inter-layer insulation film 9 formed of,for example, silicon nitride (SiN_(x)) is laminated on the firstinter-layer insulation film 8.

[0054] Next, contact holes for connecting the source/drain regions ofthe polysilicon film 6 are opened, a metallic film of, for example,aluminum (Al), titanium (Ti) is formed, and the metallic film ispatterned by etching to form a wiring 10. The wiring 10 connects thesource/drain regions of each transistor formed on the polysilicon film6, and forms a predetermined circuit pattern on the substrate.

[0055] Subsequently, a planarizing film 11 formed of, for example, anacrylic resin for planarizing the surface of the bottom gate type TFT 1is formed on the second interlayer insulation film 9 provided with thewiring 10.

[0056] Next, a transparent conductive film 12 formed of, for example,ITO for connecting the wiring 10 to external terminals or externalwirings present in the exterior is formed on the planarizing film 11after the planarizing film 11 is provided with contact holes. In theabove-described manner, the TFT 1 is fabricated.

[0057] In the method of fabricating the TFT 1 as described above, thelaser annealing apparatus 20 performs the laser annealing treatment byirradiating the surface of the amorphous silicon film with the laserlight 28 uniformized in the light intensity of the laser light 28radiated onto the surface of the amorphous silicon film, so thatdispersion of the heated and molten state of the amorphous silicon filmis restrained, and a TFT 1 uniformized in the grain diameter of crystalgrains of the polysilicon film 6 recrsytallized from the amorphoussilicon film can be obtained. In the TFT 1 obtained in this manner, thegrain diameter of the crystal grains of the polysilicon film 6 isuniformized, so that generation of nonuniformity in the form of, forexample, streaks or spots in the pictures of display devices isprevented, and transistor characteristics can be enhanced.

[0058] In addition, in the method of fabricating the TFT 1 as describedabove, the laser annealing apparatus 20 does not require an excitablegas as in a laser annealing apparatus using a conventional excimerlaser, so that the risk that the light intensity of the emitted laserlight becomes unstable due to deterioration of the excitable gas isobviated, and the surface of the amorphous silicon film can beirradiated with the laser light 28 with stable light intensity.Therefore, in the above-described method of fabricating the TFT 1, thelaser annealing apparatus 20 can subject the amorphous silicon film to alaser annealing treatment in which dispersion of heating and melting isrestrained by the laser light 28 with stable light intensity, and theyield in forming the polysilicon film 6 can be enhanced.

[0059] Further, in this method of fabricating the TFT 1, the laserannealing apparatus 20 does not need an excitable gas as in the case ofa conventional laser annealing apparatus using an excimer laser, so thatthe step of replacing the deteriorated excitable gas is not needed, andenhancement of productivity of the TFT 1 can be contrived.

[0060] Furthermore, in this method of fabricating the TFT 1, the laserannealing apparatus 20 does not need a tank for reserving the excitablegas as in the case of a conventional laser annealing apparatus using anexcimer laser, and the semiconductor laser devices 22 for emitting thelaser light 28 are comparative small in size, so that installation areacan be reduced, power consumption can be suppressed, and production costof the TFT 1 can be reduced.

[0061] In the laser annealing apparatus 20 according to the embodimentof the present invention as described above, in performing the laserannealing treatment of silicon, it is preferable that the semiconductorlaser devices 22 emit the laser light 28 with a wavelength in the rangeof 200 to 900 nm, more preferably the laser light 28 with a wavelengthof about 400 nm.

[0062] The reason is as follows. Where the wavelength of the laser light28 in the laser annealing treatment of silicon is shorter than 200 nm,in the laser annealing apparatus 20, the laser light 28 is absorbed by,for example, the atmospheric air, and the light intensity of the laserlight 28 radiated onto the surface of the amorphous silicon film islowered, so that the efficiency of the laser annealing treatment of theamorphous silicon film may be lowered.

[0063] On the other hand, where the wavelength of the laser light 28 inthe laser annealing treatment of silicon is longer than 900 nm, in thelaser annealing apparatus 20, the absorption efficiency of the amorphoussilicon film for the laser light 28 is as extremely low as not more than0.1, so that the efficiency of the laser annealing treatment of theamorphous silicon film may be lowered.

[0064] Therefore, in the laser annealing apparatus 20, in performing thelaser annealing treatment of silicon, the semiconductor laser devices 22emit the laser light 28 with a wavelength in the range of 200 to 900 nmto irradiate the surface of the amorphous silicon film therewith,whereby it is possible to achieve a laser annealing treatment in whichthe amorphous silicon film is efficiently heated and melted.

[0065] Here, the results of measurement of absorption wavelengthcharacteristics of polysilicon and amorphous silicon are shown in FIG.3. In FIG. 3, the axis of abscissas represents the wavelength of laserlight, and the axis of ordinates represents the absorption coefficientof each of polysilicon and amorphous silicon.

[0066] It is seen from the measurement results shown in FIG. 3 thatpeaks of the absorption wavelength of polysilicon and amorphous siliconare present in the vicinity of 300 nm. Particularly, it is seen thatamorphous silicon has a sufficient absorption coefficient for laserlight with a wavelength of about 400 nm which is used for the laserannealing treatment, and the laser light with a wavelength of about 400nm can be efficiently absorbed by amorphous silicon.

[0067] By this, in the laser annealing apparatus 20, when the laserannealing treatment of silicon is performed by emitting the laser light28 with a wavelength of about 400 nm from the semiconductor laserdevices 22 and irradiating the surface of the amorphous silicon filmwith the laser light 28, the laser light 28 is not absorbed by, forexample, atmospheric air, and the absorption coefficient of theamorphous silicon film for the laser light 28 is sufficiently high, sothat it is possible to achieve a laser annealing treatment in which theamorphous silicon film is efficiently heated and melted.

[0068] In addition, in the laser annealing apparatus 20, the laser light28 with a wavelength of about 400 nm used for the laser annealingtreatment of silicon is absorbed, though slightly, also into polysiliconwhere amorphous silicon and polysilicon are momentarily coexistent uponheating and melting of the amorphous silicon film, so that bothamorphous silicon and polysilicon can be simultaneously heated andmelted. Therefore, in the laser annealing apparatus 20, by the laserannealing treatment using the laser light 28 with a wavelength of about400 nm at the time of the laser annealing treatment of silicon, it ispossible to uniformize the grain diameter of the crystal grains of thepolysilicon film 6 formed through heating and melting of the amorphoussilicon film.

[0069] While the TFT 1 is of the bottom gate structure comprising thegate electrode 3 on the lower side of the polysilicon film 6 in theembodiment as described above, this structure is not limitative, and,for example, a top gate structure comprising a gate electrode on theupper side of a polysilicon film may also be adopted.

[0070] In the case of uniformizing the light intensity of the laserlight 28 radiated onto the surface of the amorphous silicon film, aconstitution in which the plurality of semiconductor laser devices 22are supported on the support base 23 so that the emitting portions 29for emitting the laser light 28 are disposed parallel to the surface ofthe amorphous silicon film has been adopted in the embodiment asdescribed above, this constitution is not limitative, and, for example,constitutions of the laser annealing apparatus as shown in FIGS. 4 to 8may also be adopted. In the following description of the laser annealingapparatuses shown in FIGS. 4 to 8, the same or equivalent constitutions,portions and functions as or to those of the above-described laserannealing apparatus 20 will be denoted by the same symbols in thefigures and description thereof will be omitted.

[0071] First, a laser annealing apparatus 40 shown in FIG. 4 will bedescribed. The laser annealing apparatus 40 has a constitution in whicha plurality of support bases 23 each for supporting a plurality ofsemiconductor laser devices 22 in series at predetermined intervals inparallel to the surface of an amorphous silicon film, on the upper sideof a glass substrate 2, are arranged in a direction roughly orthogonalto the direction in which the plurality of semiconductor laser devices22 are arranged.

[0072] In the laser annealing apparatus 40 constituted as above, at thetime of uniformizing the light intensity of the laser light 28 radiatedonto the surface of the amorphous silicon film, for example, theplurality of semiconductor laser devices 22 are supported on the supportbases 23 so that emitting portions 29 for emitting the laser light 28are disposed parallel to the surface of the amorphous silicon film,whereby the distances between the emitting portions 29 of the pluralityof semiconductor laser devices 22 and the surface of the amorphoussilicon film are made to be constant.

[0073] By this arrangement, in the laser annealing apparatus 40, thesurface of the amorphous silicon film can be irradiated with the laserlight 28 with stable light intensity, and a laser annealing treatmentfor heating and melting the amorphous silicon film without dispersioncan be achieved.

[0074] In addition, in the laser annealing apparatus 40, the pluralityof support bases 23 each for supporting the plurality of semiconductorlaser devices 22 are arranged, so that the area of irradiation of thesurface of the amorphous silicon film with the laser light 28 isenlarged. Also, for example, the region needing irradiation with thelaser light 28 can be irradiated, at a stroke, with the laser light 28uniformized in the light intensity of the laser light 28 radiated ontothe surface of the amorphous silicon film. Therefore, the time requiredfor the laser annealing treatment can be shortened, and productivity ofthe TFT 1 can be enhanced.

[0075] Next, a laser annealing apparatus 50 shown in FIG. 5 will bedescribed. The laser annealing apparatus 50 has a constitution in whichoptical devices 51 such as microlenses for forming the beam shape oflaser light 28 to a predetermined shape are fitted respectively toemitting portions 29 for emitting the laser light 28 of a plurality ofsemiconductor laser devices 22. The optical device 51 forms the laserlight 28 incident thereon from one main surface side thereof to apredetermined beam shape and emits it from the other main surface sidethereof.

[0076] In the laser annealing apparatus 50 constituted as above, inuniformizing the light intensity of the laser light 28 radiated onto thesurface of an amorphous silicon film, for example, the plurality ofsemiconductor laser devices 22 are supported on a support base 23 sothat the main surfaces for emitting the laser light 28 of the opticaldevices 51 fitted to the plurality of semiconductor laser devices 22 aredisposed parallel to the surface of the amorphous silicon film, wherebythe distances between the main surfaces for emitting the laser light 28of the optical devices 51 and the surface of the amorphous silicon filmare made to be constant.

[0077] By this arrangement, in the laser annealing apparatus 50, thesurface of the amorphous silicon film can be irradiated with the laserlight 28 with stable light intensity, and a laser annealing treatmentfor heating and melting the amorphous silicon film without dispersioncan be achieved.

[0078] In addition, in the laser annealing apparatus 50, the laser light28 is formed into the predetermined beam shape by the optical devices51, so that the laser light 28 uniformized in the light intensity of thelaser light 28 radiated onto the surface of the amorphous silicon filmcan be radiated onto only a predetermined region of the amorphoussilicon film. Therefore, needless irradiation with the laser light 28can be omitted, so the productivity of the TFT 1 can be enhanced.

[0079] Next, a laser annealing apparatus 60 shown in FIG. 6 will bedescribed. This laser annealing apparatus 60 comprises a support base 61for supporting a plurality of semiconductor laser devices 22 at aposition spaced away from a moving stage 21, optical fibers 62 forguiding the laser light 28 emitted from the semiconductor laser devices22, and an optical fiber support base 63 for supporting the opticalfibers 62.

[0080] The support base 61 supports the plurality of semiconductor laserdevices 22, in which emitting portions 29 for emitting the laser light28 are directed in a predetermined direction, in series at predeterminedintervals.

[0081] The optical fibers 62 are each in the form of a flexible thinline, one end side thereof are fitted respectively to emitting portions29 for emitting the laser light 28 of the plurality of semiconductorlaser devices 22, the laser light 28 emitted from the emitting portions29 are guided through the inside of the thin lines, and the laser light28 thus guided is emitted from emitting port portions 62 a which are theother end side of the thin lines. In the optical fiber 62, the other endfaces as the emitting port portions 62 a are made to be, for example, ina convex form, whereby the emitted laser light 28 can be formed into apredetermined beam shape.

[0082] The optical fiber support base 63 supports portions near theemitting port portions 62 a of the optical fibers 62 so that theemitting port portions 62 a of the optical fibers 62 are opposed inparallel to the surface of the amorphous silicon film and that theemitting port portions 62 a of the optical fibers 62 are arranged inseries at predetermined intervals on the surface of the amorphoussilicon film. In addition, the optical fiber support base 63 comprises alift mechanism (not shown) for moving the supported optical fibers 62 upand down in the vertical direction indicated by arrows S in the figurerelative to a moving stage 21. The lift mechanism is capable ofregulating the distance between the emitting port portions 62 a of theoptical fibers 62 and the surface of the amorphous silicon film, so thatthe light intensity of the laser light 28 emitted from the emitting portportions 62 a of the optical fibers 62 and radiated onto the surface ofthe amorphous silicon film can be varied.

[0083] In the laser annealing apparatus 60 constituted as above, inuniformizing the light intensity of the laser light 28 radiated onto thesurface of the amorphous silicon film, for example, the portions nearthe emitting port portions 62 a of the optical fibers 62 are supportedby the optical fiber support base 63 so that the emitting port portions62 a of the optical fibers 62 fitted to the plurality of semiconductorlaser devices 22 are disposed parallel to the surface of the amorphoussilicon film, whereby the distances between the emitting port portions62 a of the optical fibers 62 and the surface of the amorphous siliconfilm are made to be constant.

[0084] By this arrangement, in the laser annealing apparatus 60, thesurface of the amorphous silicon film can be irradiated with the laserlight 28 with stable light intensity, and a laser annealing treatmentfor heating and melting the amorphous silicon film without dispersioncan be achieved.

[0085] In addition, in the laser annealing apparatus 60, the opticalfibers 62 are flexible, and the position of irradiating the amorphoussilicon film with the laser light 28 can be easily varied, so that theregion and position of irradiation with the laser light 28 can be easilycontrolled according to the size of the amorphous silicon film.

[0086] Further, in the laser annealing apparatus 60, the optical fibers62 can be supported by the optical fiber support base 63 in thecondition where portions near the emitting port portions 62 a of theoptical fibers 62 are bundled, as shown in FIG. 7. In this case, in thelaser annealing apparatus 60, the laser light 28 emitted from theemitting port portions 62 a of the optical fibers 62 can be radiatedonly onto a predetermined region of the amorphous silicon film, wherebyneedless irradiation with the laser light 28 can be omitted, andproductivity of the TFT 1 can be enhanced.

[0087] Furthermore, in the laser annealing apparatus 60, for example,the semiconductor laser devices 22 can be disposed remote from the glasssubstrate 2, so that component parts and the like can be easilyreplaced.

[0088] Next, a laser annealing apparatus 70 shown in FIG. 8 will bedescribed. The laser annealing apparatus 70 comprises a moving stage 71for mounting a glass substrate 2 thereon, a support base 72 forsupporting a plurality of semiconductor laser devices 22 at a positionremote from the moving stage 71, an optical device 73 for forming thelaser light 28 emitted from the semiconductor laser devices 22 into apredetermined beam shape, and a reflector 74 for reflecting the laserlight 28 transmitted through the optical device 73 onto the surface ofthe amorphous silicon film.

[0089] The moving stage 71 is high in flatness of its main surface onwhich to mount the glass substrate, and has the function of moving theglass substrate 2 mounted thereon to a position for the laser annealingtreatment and the function of fixing the glass substrate 2.

[0090] In concrete, the moving stage 71 comprises an X stage 75, a Ystage 76, a Z stage 77, and a sucker mechanism which is not shown. The Xstage 75 and the Y stage 76 are stages for horizontally moving themoving stage 71 in directions of arrows T and arrows U in the figure inthe plane of the main surface thereof, thereby moving the mounted glasssubstrate 2 in mutually roughly orthogonal directions and guiding theglass substrate 2 to a position for the laser annealing treatment. The Zstage 77 is a stage capable of moving in the vertical directionindicated by arrows V in the figure relative to the mounted glasssubstrate 2, thereby regulating the height of the moving stage 71. Bythis arrangement, with the Z stage 77, the light intensity of the laserlight 28 reflected by the reflector 74 and radiated onto the surface ofthe amorphous silicon film can be varied. The sucker mechanism is forfixing the glass substrate 2 by sucking the glass substrate 2 onto themain surface of the moving stage 71.

[0091] The support base 72 supports the plurality of semiconductor laserdevices 22 in the condition where the plurality of semiconductor laserdevices 22 with the emitting portions 29 for emitting the laser light 28directed in a predetermined direction are arranged in series atpredetermined intervals.

[0092] The optical device 73 is an optical mechanism, for example, abeam homogenizer, on which the laser light 28 emitted from the pluralityof semiconductor laser devices 22 is incident from one main surface sidethereof, and from which the laser light 28 is emitted from the othermain surface side in the state of being formed into a predetermined beamshape.

[0093] The reflector 74 has a reflective surface 74 a for reflecting thelaser light 28 formed into the predetermined beam shape by the opticaldevice 73. The reflector 74 is disposed on the upper side of the surfaceof the amorphous silicon film so that the position of impingement of thelaser light 28 on the reflective surface 74 a is parallel to the surfaceof the amorphous silicon film. By this arrangement, with the reflector74, the laser light 28 formed into the predetermined beam shape by theoptical device 73 can be reflected so as to be radiated onto the surfaceof the amorphous silicon film.

[0094] In the laser annealing apparatus 70 constituted as above, inuniformizing the light intensity of the laser light 28 radiated onto thesurface of the amorphous silicon film, for example, the position ofimpingement of the laser light 28 on the reflective surface 74 a is setparallel to the surface of the amorphous silicon film, whereby thedistance between the position of impingement of the laser light 28 onthe reflective surface 74 a and the surface of the amorphous siliconfilm is made to be constant.

[0095] By this arrangement, in the laser annealing apparatus 70, thesurface of the amorphous silicon film can be irradiated with the laserlight 28 with stable light intensity, and a laser annealing treatmentfor heating and melting the amorphous silicon film without dispersioncan be achieved.

[0096] In addition, in the laser annealing apparatus 70, for example,the semiconductor laser devices 22, the optical device 73 and the likecan be disposed remote from the glass substrate 2, so that thesecomponent parts can be easily replaced.

[0097] The laser annealing apparatuses with various constitutions asdescribed above in the embodiments of the present invention are notlimited to the above-described constitutions. For example, aconstitution in which the optical fibers and the optical device are usedjointly may be adopted.

What is claimed is:
 1. A laser annealing apparatus for subjecting amaterial to an annealing treatment by irradiating the surface of saidmaterial with laser light, comprising: a plurality of semiconductorlaser devices for emitting said laser light towards said material, anduniformizing means for uniformizing the light intensity of said laserlight emitted from said plurality of semiconductor laser devices andradiated onto said surface of said material.
 2. A laser annealingapparatus as set forth in claim 1, wherein said uniformizing meansarranges said plurality of semiconductor laser devices on the upper sideof said surface of said material so that emitting portions for emittingsaid laser light of said plurality of semiconductor laser devices andsaid surface of said material are opposed to each other.
 3. A laserannealing apparatus as set forth in claim 1, wherein said uniformizingmeans comprises an optical device which guides said laser light emittedfrom said plurality of semiconductor laser devices and which has anemitting port portion for emitting said guided laser light in apredetermined direction, and said optical device is so disposed thatsaid emitting port portion and said surface of said material are opposedto each other.
 4. A laser annealing apparatus as set forth in claim 1,wherein said uniformizing means comprises an optical device whichtransmits therethrough said laser light emitted from said plurality ofsemiconductor laser devices to thereby form the beam shape of said laserlight into a predetermined shape and which has an emitting port portionfor emitting said laser light with said predetermined beam shape in apredetermined direction, and said optical device is so disposed thatsaid emitting port portion and said surface of said material are opposedto each other.
 5. A laser annealing apparatus as set forth in claim 1,wherein said uniformizing means comprises an optical device forreflecting said laser light emitted from said plurality of semiconductorlaser devices to a predetermined direction, and said optical device isdisposed on the upper side of said surface of said material.
 6. A methodof fabricating a thin film transistor, comprising: a first step offorming an amorphous silicon film on a substrate, a second step ofsubjecting said amorphous silicon film to an annealing treatment tothereby convert said amorphous silicon film into a polycrystallinesilicon film, and a third step of laminatingly fabricating said thinfilm transistor in a predetermined region with said polycrystallinesilicon film as an active layer, wherein in said second step, a laserannealing apparatus comprising a plurality of semiconductor laserdevices for emitting laser light subjects said amorphous silicon film tosaid annealing treatment by irradiating the surface of said amorphoussilicon film with said laser light uniformized in the light intensity ofsaid laser light radiated onto said surface of said amorphous siliconfilm by uniformizing means for uniformizing the light intensity of saidlaser light radiated onto said surface of said amorphous silicon film,whereby said amorphous silicon film is heated, melted and recrystallizedto be thereby converted into said polycrystalline silicon film.
 7. Amethod of fabricating a thin film transistor as set forth in claim 6,wherein in said second step, said uniformizing means arranges saidplurality of semiconductor laser devices on the upper side of saidsurface of said amorphous silicon film so that emitting portions foremitting said laser light of said plurality of semiconductor laserdevices and said surface of said amorphous silicon film are opposed toeach other.
 8. A method of fabricating a thin film transistor as setforth in claim 6, wherein in said second step, said uniformizing meanscomprises an optical device which guides said laser light emitted fromsaid plurality of semiconductor laser devices and which has an emittingport portion for emitting said guided laser light in a predetermineddirection, and said optical device is so disposed that said emittingport portion and said surface of said amorphous silicon film are opposedto each other.
 9. A method of fabricating a thin film transistor as setforth in claim 6, wherein in said second step, said uniformizing meanscomprises an optical device which transmits therethrough said laserlight emitted from said plurality of semiconductor laser devices tothereby form the beam shape of said laser light into a predeterminedshape and which has an emitting port portion for emitting said laserlight with said predetermined beam shape in a predetermined direction,and said optical device is so disposed that said emitting port portionand said surface of said amorphous silicon film are opposed to eachother.
 10. A method of fabricating a thin film transistor as set forthin claim 6, wherein in said second step, said uniformizing meanscomprises an optical device for reflecting said laser light emitted fromsaid plurality of semiconductor laser devices to a predetermineddirection, and said optical device is disposed on the upper side of saidsurface of said amorphous silicon film.